It is a hard truth to swallow, but nature does not care if we live or die. We cannot survive without the oceans, for example, but they can do just fine.

It is a hard truth to swallow, but nature does not care if we live or die.

We cannot survive without the oceans,for example, but they can do just fine without us.

Roger Rosenblatt

Water Pollution

Chapter 20

Water Pollution Comes from Point and Nonpoint Sources

• Water pollution • Point sources– Located at specific places– Easy to identify, monitor, and regulate– Examples

• Nonpoint sourcesBroad, diffuse areasDifficult to identify and controlExpensive to clean upExamples

Cont’d

• Agriculture activities: leading cause of water pollution– Sediment eroded from the lands– Fertilizers and pesticides– Bacteria from livestock and food processing wastes

• Industrial facilities• Mining

• Other sources of water pollutionParking lotsHuman-made materials

E.g., plastics

Climate change due to global warming

1

2

3

Major Water Pollutants and Their Sources

Streams Can Cleanse Themselves If We Do Not Overload Them

• Dilution

• Biodegradation of wastes by bacteria takes time

• Oxygen sag curve

Cultural Eutrophication Is Too Much of a Good Thing

• Eutrophication• Oligotrophic lake– Low nutrients, clear water

• Cultural eutrophication

• During hot weather or droughts– Algal blooms– Increased bacteria– More nutrients– Anaerobic bacteria

• Then what?

C & N added

C , N & P added

Using Laws to Protect Drinking Water Quality

• 1974: U.S. Safe Drinking Water Act– Sets maximum contaminant levels for any pollutants that

affect human health

Ocean Pollution Is a Growing and Poorly Understood Problem

• 2006: State of the Marine Environment– 80% of marine pollution originates on land– Sewage– Coastal areas most affected

Cont’d

• Cruise line pollution: what is being dumped?

• U.S. coastal waters– Raw sewage – Sewage and agricultural runoff: NO3

- and PO43-

– Harmful algal blooms– Oxygen-depleted zones

Solutions: Coastal Water Pollution, Prevention and Cleanup

Solutions:We Need to Reduce Surface Water Pollution from Nonpoint

Sources

• Reduce erosion– Keep cropland covered with vegetation

• Reduce the amount of fertilizers

• Plant buffer zones of vegetation

• Use organic farming techniques

Solutions

• Use pesticides prudently

• Control runoff

• Tougher pollution regulations for livestock operations

• Deal better with animal waste

Laws Can Help Reduce Water Pollution from Point Sources

• 1972: Clean Water Act

• EPA: experimenting with a discharge trading policy

• Could this allow pollutants to build up?

Sewage Treatment Reduces Water Pollution

• Wastewater or sewage treatment plants– Primary sewage treatment• Physical process

– Secondary sewage treatment• Biological process

– Tertiary or advance sewage treatment • Bleaching, chlorination

Solutions: Primary and Secondary Sewage Treatment

Solutions: Water Pollution, Methods for Preventing and Reducing Water Pollution

What Can You Do? Water Pollution, Ways to Help Reduce Water Pollution